Acetate provokes mitochondrial stress and cell death in Ustilago maydis

The fungal pathogen Ustilago maydis causes disease on maize by mating to establish an infectious filamentous cell type that invades the host and induces tumours. We previously found that β-oxidation mutants were defective in virulence and did not grow on acetate. Here, we demonstrate that acetate inhibits filamentation during mating and in response to oleic acid. We therefore examined the influence of different carbon sources by comparing the transcriptomes of cells grown on acetate, oleic acid or glucose, with expression changes for the fungus during tumour formation in planta. Guided by the transcriptional profiling, we found that acetate negatively influenced resistance to stress, promoted the formation of reactive oxygen species, triggered cell death in stationary phase and impaired virulence on maize. We also found that acetate induced mitochondrial stress by interfering with mitochondrial functions. Notably, the disruption of oxygen perception or inhibition of the electron transport chain also influenced filamentation and mating. Finally, we made use of the connections between acetate and β-oxidation to test metabolic inhibitors for an influence on growth and virulence. These experiments identified diclofenac as a potential inhibitor of virulence. Overall, these findings support the possibility of targeting mitochondrial metabolic functions to control fungal pathogens.

Determination of acyl-CoA esters and acyl-CoA synthetase activity in mouse brain areas by liquid chromatography-electrospray ionization-tandem mass spectrometry

The acyl-CoA levels and the acyl-CoA synthetase activities in 7 areas of mouse brain were determined by liquid chromatography-electrospray ionization-tandem mass spectrometry. Twenty-one acyl-CoA esters of C2:0, C4:0, C6:0, C8:0, C10:0, C12:0, C14:1, C14:0, C16:0, C16:1, C18:0, C18:1, C18:2, C18:3, C20:0, C20:4, C20:5, C22:0, C22:5, C22:6 and C24:0 were detected in the olfactory bulb, cerebral cortex, hippocampus, cerebellum, hypothalamus, midbrain and medulla oblongata. The brain areas contained primarily the acyl-CoAs of the C16:0, C18:0, C18:1, C20:4 and C22:6 species. The relative abundances of the acyl-CoAs of C16:0, C18:0 and C18:1 were considerably higher than those of C20:4 and C22:6. The levels of medium-chain acyl-CoAs were only 1.2% that of the long-chain acyl-CoAs. The differences in the acyl-CoA synthetase activities in each area of mouse brain were less dramatic. The order of the acyl-CoA synthetase activities for fatty acids of different chain lengths was palmitic acid>arachidonic acid>docosahexaenoic acid>octanoic acid. The analytical method proved to be very useful for the analysis of the acyl-CoA profile of tissues. Our results have important implications for understanding the regulation of acyl-CoA synthetase activity and long-chain fatty acid turnover in the phospholipids in the brain.